Loud-speaker mounting



April 24, 1951 s. E. LEVY LOUD-SPEAKER MOUNTING 6 Sheets-Sheet 1 Filed Feb. 8, 1946 INVENTOR SIDNEY E. LEVY ATTORNEY April 24, 1951 s. E. LEVY LOUD-SPEAKER MOUNTING e Sheets-Sheet 2 Filed Feb. 8, 1946 INVENTOR SIDNEY E. LEVY &

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ATTORNEY April 24, 1951 s. E. LEVY LOUD-SPEAKER MOUNTING 6 Sheets-Sheet 4 Filed Feb. 8, 1946 INVENTOR vl V E L L Y E N D ATTORNEY April 24, 1951 s. E. LEVY LOUD-SPEAKER MOUNTING 6 Sheets-Sheet 5 Filed Feb. 8, 1946 INVENTOR SlDNEY 51.5w BYAQ I 9 5 ATTORNEY 6 Sheets-Sheet 6 S. E. LEVY LOUD-SPEAKER MOUNTING INVENTOR ATTORNEY April 24, 1951 Filed Feb. 8, 1946 SIDNEY E. LEVY Patented Apr. 24, 1951 2,550,359 LOUD-SPEAKER 'MOUNTING Sidney E. Levy, Brooklyn, N. Y., assignor, by mesne assignments to University Loudspeakers, Inc., New York, vN. Y., a corporation of New York Application February 8, 1946, Serial *No. 646;417

4 Claims.

1 An object of my invention is to providea compact, efficient, and economical loud speaker.

A particularfeature of-my invention is theprvisionrof a mixingchamber for connecting a ,p1u rality of driving units to a horn, or a plurality of hornsto a driving unit,.in which the tone arms or sound channelsofsaid mixing chamber are allin the same plane; that is, strictly'speaking, between closely'spaced parallel planes.

Another'featureof my invention isna-single flat member, which may be :a casting, containing a plurality of tone arms.

Another feature of 'my invention is the provision of an insulated flange between a driving unit and a mixing chamber forthe purpose of improving the dielectric strength between the winding of the driver-and the said chamber which represents agrounding member common'to all drivers.

'Another feature of my invention is the provision of means for preventing the separation or insecurity of a driving unit from a mixing chamber or flange.

Another feature of my inventionris the provision of an electrical .circuit and apparatus: permitting a plurality of'voicecoi-ls to beconnected in "series without affecting the operation of the remainder'of the units if'the voice coil of one unit should become open-circuite'd.

'In the "construction of loud speakers it has heretofore been the practice where-twoor more driving units are'to be connected to a single horn-*to use connectors providing individual tone arms or sound channels from the driving units to the horn, which'i'n'dividual arms diverge at various awkward angles. A unit thus'constructed is'awkwar'd to' handle and install, ungainly in appearance, susceptible to' mechanical shocks, and expensive.

I have discovered that it is possible to provide a tone arm connecting a driving unit with a loud speaker havingtherein two right angle bends in opposite directions with no'appreciable loss in quality, provided'the difference in distance around the bends does not exceed one-quarter wave lengthfor the highest frequency to be reproduced. I 'have'noticed that actual bends may be made short enough so that the losses dueto a bend fall outside of the useful frequency range so that, in efiect thereis no loss ofquality. This makes it possible to produceasingle substantially flat casting having'a' plurality of tone arms and thus produce .a, compact; -.efilcient,- faithful, and rugged loud speakerwhichzis pleasing in'appearance at less expense than heretofore.

In the drawings- Figure 1 is a plan view of a central castingor mixing chamber designed for six driving units to be connected through the tone arms of the mixing chamber to a horn;

Figure 2 is a section along the line 22 OfFig-e ure 1;

Figure 3 is a partial planview of:.the center of the reverse side of the mixing chamber of Figure Fi1gure4 is a sectionalong the line .4-.-.-..4 of 'Figure Figure 5 is a plan viewof the gasket shown partially at the center of Figure3;

Figure 6 isa-planview ofia flange for connecting a driving unit to themixing chamber-ofFigure Figure 7 is an elevation of the flange of Figure Figure 8 is a section of Figure 7 along the lines l--1 thereof;

Figure 9 is a schematic plan view of a-mixing chamber designed to accommodate twelve driving units to be connectedtoa horn;

Figure 10 isasection along the linestD-lllof FigureQ;

Fig. 11 issa'section showing a modification of the device of Figures 9-and l0;

Figure 12 is .a schematic: plan viewof--a.-mix' ing chamber designed to accommodateeighteen driving units for connection to a single horn;

Figure 13 is a section along the lines l 3--l- 3 of Figure 12;

Figure 14 is a :section illustrating a modification of Figure 1;

Figure 15 is a sectional -view illustrating another modification of my invention in which there is a single driving unit and two horns or vice versa; and

Figure 16 is a circuitdiagram illustratingrthe connection of a variable impedance coilinshunt to a plurality of series connected voicercoils.

In Figures 1, 2, and 3 there. is acentral casting or mixing chamber I having therein six tone arms 2, 3, 4, 5, and"6, each terminatingatan opening in thesurface of the mixing chamber which openings are numbered, respectively, 1, 8,9, H), H, and I2. Onedriving unit. I3 is shown placed in position on the mixing chamber and in Figure 1 a flange 14 is shown in position over the opening 8 to accommodate a secondidriving unit. Additional driving units would be similarly placed over the openings 9 to l2. The various tone arms converge to separatepcentral openings l5, [6, [1,18, l9,.and 20 .separateduby partitions in the central casting which partitions join at the center 2|. Said partitions could be replaced by a plug which would serve the purpose of said partitions. A horn 22 may be mounted with its throat over the openings 15 to 20 and separated from the mixing chamber l by a gasket 23.

The mounting of the individual driving units is best shown in Figure 2 where it may be seen that there is an insulating gasket 24 separating a flange 25 from the mixing chamber 1 and insulating it therefrom. The flange 25 is held in position by means of bolts 26 and 21 illustrated in Figure 1. These bolts are surrounded by insulating collars and have insulating washers under their heads so there will be no electrical connection between the flanges such as flanges l4 and 25 and the mixing chamber 1. The flanges are internally threaded to accommodate external threads on the driving units, such as driving unit i3, which driving units are therefore screwed into position.

An ear 28 on the flange '25 is tapped to accommodate a set screw 29 which holds the driving unit firmly in position. The surface of the driving unit may be roughened or ribbed to provide positive holding action for the set screw 29.

A watertight coupling 30, Figure 4, is provided to permit the entry of the electrical cable 3| carrying the current to the voice coils illustrated in Figure 16 which will be hereafter explained. A connecting plug 32 connects the electric cable from the amplifier.

Referring to Figure 2 it will be seen that the tone arm 2 has in it two right angle bends in opposite directions. Each of the tone arms 2 to 6 is identical and the description of the tone arm 2 therefore applies to all. As the sound pressure wave travels from the driving unit iii to the horn 22 it will have a shorter path around the inner bend adjacent the opening I from point a to point b than around the outer surface of the bend from point at to point e. The front of the sound pressure wave will therefore not be perpendicular to the face of the mixing chamber I as it travels along the tone arm after passing this bend. When this sloping wave front reaches the second right angle bend adjacent the opening I it will have a shorter path to travel around the inner face of this bend from point to point 9 than around the outer face of the bend from point it to point 2'. However, as this bend is in the opposite direction to the first, the front of the pressure wave will be restored so that as it emerges from the opening it will be parallel to the face of the casting l at this point.

As before explained, the difference in the distance around the bends, that is the difference in the distance between points a and b and the distance between points d and e (and similarly the difference in distance between points 1 and g and the distance between points It and i) must not exceed one-quarter of a wave length for the highest frequency the apparatus is capable of reproducing. In other words there will be no less of frequency below the frequency for which the difference in this distance is less than onequarter wave length. Actually, in apparatus which has been constructed in accordance with this application such losses fall outside of the useful frequency range so that there is no loss of quality by reason of these bends. I am thus able to provide a mixing chamber consisting of a single casting having therein a plurality of 4 tone arms all in the same plane, resulting in the above mentioned advantages.

It has been stated above that the flanges such as flange 25, and accordingly the driving units such as [3, are all electrically insulated from the central casting or mixing chamber I. By thus insulating the driving units from the mixing chamber and from one another I am able to connect the voice coils of the driving units in series. Because such series connection results in higher terminal voltage (for a given power input) the insulating flanges prevent high voltage arcing across the voice coil gaps. Such a series connection is illustrated in Figure 16 where the electrical input wires 33 and 34, shown in Figure 4, are again shown with the voice coils 35 to 40 connected in series across these two leads. In shunt with the series connected voice coils is a variable impedance coil 4| having a plurality of taps connected to points between successive voice coils so that successive sections of the coil are in parallel with the individual voice coils. This variable impedance 4| is designed to absorb power if one of the voice coil units should open up. The impedance of each section of coil 4| is high with respect to the voice coil with which it is in shunt when the circuits are all complete. If one voice coil should become open-circuited a heavier current passes through the turns of the coil 4| shunted by that voice coil, causing the impedance of that particular section to decrease to equal the impedance of the voice coil which it replaces. If one of the voice coils should become opencircuited, therefore, the remainder will operate the same as before. By this arrangement I am able to use a high voltage audio current across the leads 33 and 34 which' voltage is equal to the sum of the series voltages through the voice coils 35 to 40. This permits the use of a higher impedance generator, namely the audio amplifier, and therefore the connecting lines between amplifier and loud speaker may then be of smaller gauge wire.

Instead of a single tapped reactor 4|, individual reactors could be used for each driver unit.

Figures 1 to 8 have been described in connec-- tion with the use of six driving units and one horn. It will be understood of course that the arrangement is not limited to six units but may use more or less, and the units may be reversed,

that is, one large driving unit may be used to replace the horn 22 and six horns to replace the driving units l3, etc.

Figures 9 and 10 illustrate a modification of my invention in which twelve driving units are used with a single horn, the successive driving units being on opposite sides of the central casting or mixing chamber. That is, the central casting or mixing chamber 45 has mounted thereon twelve driving units'such as 41, 48, 49 and 50, six of the driving units such as 41 and 49 being mounted on one face and'the other six such as 48 and 50 being mounted on the opposite face. Each driving unit communicates with a tone arm such as 5|, 52, 53, 54, and 55 terminating in a central opening shown in face view in Figure 9 over which is mounted a horn 5B.

In this case it will be noted that while six of the tone arms such as 55 have two right angle bends in opposite directions and thus follow the principles explained above for avoiding loss of high frequencies, the remaining tone arms such as 5|, 53 have two right angle bends in the same direction and therefore. apparently violate the principles set forth above. Actually, there may be some loss of high frequencies in the tone arms connecting the horn with driving units mounted on the same side of the mixing chamber and such loss may extend down into the useful frequency range. However, any frequencies which may be lost from'these six driving units will be present from the driving units such as 41 and 50 mounted on the opposite side of the mixing chamber from the horn 56, so that these frequencies will actually be present in the output though to a lesser volume in proportion to lower frequencies than if all twelve driving units were mounted on the opposite side of the horn so that all tone arms had their bends in opposite directions in accordance with the principles explained above. Thus, the presence of six driving units on the opposite-side of the mixing chamber from the horn providing a full tonal range, provides the highest frequencies desired in sufficient quantity to make it possible to use six additional driving units on the same side with the horn with a quality of performance that is thoroughly satisfactory and, indeed, for most purposes indistinguishable from a condition in which the entire range from all driving units was reproduced. By staggering the units on oppositesides of the mixing chamber it isfpossible to make the structure more compact and to attain certain mechanical advantages.

In the case of the structure of Figures 9 and 10 the units and horn may also be reversed. That is, here again a single driving unit may be used at the position where the horn is shown, and twelve horns used at the positions where the driving units are shown, where this arrangement is necessary or desirable for acoustic directivity or some other reason.

I may also use a mixing chamber with tone arms all of which bend in the same direction, so that the horn and all driving units will be on the same face of the mixing chamber. While this will introduce some losses, as explained above, this construction may be used in cases where such losses may be tolerated and mechanical convenience makes it desirable.

Figure 11 shows a modification of my device in which there is again a central casting or mixing chamber 51 having a plurality of tone arms in a single plane, but in this case the driving units on opposite faces of the central casting are mounted opposite one another with the tone arms from opposed driving units merging into a single tone arm such as 58 and 59, and supplying a horn 60. One pair of opposed driving units is shown at El and 62 and another pair at 53 and 64. Any desired number of driving units may be used and the particular apparatus shown in Figure 11 is designed to illustrate the use of twelve such driving units, six on each face. A baffle such as 65 and 56 is cast into the mixing chamber 51 to deflect the sound pressure from the driving units so that the pressures of opposed units are traveling in the same direction as they join.

Here again the horn might be replaced by a '61 withtone armssuch asil-5 and 16 .c'astintdthe mixingi'chamberfi'l from the peripheryto communicate between the .lperipheral driving units and the :horn Tl. A plurality .of cast-in baffles such-as 18, i9, 8fl,iand 8| deflect the sound waves so that'they are all traveling in the same direction at the time they join. The 'distancefrom each driving unit'to the horn is'the same so that thesound pressure wave from each three driving units feeding a common tone arm, as well'as from another driving'units, is in phase.

This modification employs the same principles which have been discussed in connection with the earlier figures so that no further discussion is necessary at this time. It may be noted, however, that here again all tone arms are in the same plane, and the number of driving'units isnot necessarily limited to the number showneither as the maximum or minimum. Here again-asin the previous figures, the horn may be replaced with a single driving unit and the driving units replaced with horns.

Although 'I have shown in this modification driving units mounted directly opposite one anotherythe driving units on opposite faces may be staggered as in the case of Figures 9 and 10, with a separate tone arm for each face mounted driving unit, and the peripheral driving units may also be staggered between two adjacent driving units which are mounted on opposite faces, with an individual tone arm for each peripherally mounted unit.

In Figure 14 I have illustrated a reverse arrangement to that shown in Figures 1 and 2. That is, I have illustrated a single driving unit 82 supplying two or more horns 83, 84, through tone arms in a single plane formed as a part of thefiat central casting or mixing chamber I.

In Figure 15 I have illustrated another arrangement in which a single driving unit 85 supplies two horns 86, 81, through a central casting 88 having a common tone arm 89 connecting the driving unit with the horns, and with a baiile 90 directing the air pressure to the horns. This represents a simplification of my basic idea as applied to a unit having only two horns; or, again, a single horn may be used to replace the driving unit 85 and two driving units used to replace the horns 86, 81. A single symmetrical casting such as 88, having a central common tone arm, has the great advantage of being able to be mounted upon a lathe for threading and machining.

It will be obvious to those skilled in the art that my invention is capable of various modifications and I do not desire to be restricted there fore to the particular details shown and described but only within the scope of the appended claims.

What is claimed is:

1. A loud speaker comprising a flat generally plate-like member having radially extending passageways therein acting as tone arms, said passageways extending from points spaced about the center of said plate-like member on one face surface thereof to points adjacent the periphery of said plate-like member on both face surfaces thereof, said passageways being substantially identical each to the other.

2. A loud speaker comprisin a flat generally circular plate-like member having a plurality of radially extending passageways therein acting as tone arms, alternate ones of said passageways extending from points spaced about the center of said member on one face surface thereof to points on the same face surface adjacent the periphery and the others of said passageways extending from points spaced about the center on the said one face surface of said plate-like member to points adjacent the periphery on the other face surface of said member, said passageways being substantially identical each to the other.

3. A loud speaker comprising a flat generally plate-like member having radially extending passageways therein acting as tone arms, said passageways extending from points spaced about the center of said plate-like member on one face surface thereof to points adjacent the periphery of said plate-like member on both face surfaces thereof, said passageways being substantially identical each to the other, and a horn fixed to said plate-like member, one end of said horn member encompassing the open ends of the passageways adjacent the center of said plate-like member.

4. A loudspeaker comprising a flat generally plate-like member having radially extending passageways therein acting as tone arms, said passageways extending from points spaced about the center of said plate-like member on one face surface thereof to points adjacent the periphery of said plate-like member on both face surfaces thereof, said passageways being substantially identical each to the other, said passageways also extending to the peripheral surfaces of said platelike member.

SIDNEY E. LEVY.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 324,728 Perrin Aug. 18, 1885 893,286 Turner July 14, 1908 1,129,792 Cole Feb. 23, 1915 1,469,941 Kuen Oct. 9, 1923 1,516,060 Rhamstine Nov. 18, 1924 1,578,595 Frantz Mar. 30, 1926 1,718,353 Hutchison June 25, 1929 1,753,812 Thomas Apr. 8, 1930 I 1,770,491 Minton et a1. July 15, 1930 1,825,166 Sullivan Sept. 29, 1931 2,089,391 Marion Aug, 10, 1937 2,094,681 Sears' Oct. 5, 1937 2,146,325 Allison Feb. 7, 1939 2,224,000 Morgan Dec. 3, 1940 2,435,535 Eaves Feb. 3, 1948 2,458,038 Volkmann Jan. 4, 1949 FOREIGN PATENTS Number Country Date 221,860 Germany May 11, 1910 477,113 Germany May 16, 1929 

